Some amino alcohols may be represented by the general formula:
These amino alcohols can be valuable materials because they may be used as solvents, intermediates for making surface active agents, corrosion inhibitors in metal working fluids, neutralizing agents in acid scrubbing during natural gas or syngas purification processes, and aids in the preparation of compounds for use in the pharmaceutical industry.
Currently, processes exist for the preparation of amino alcohols, such as amino alcohols with the general formula set forth herein. Such processes can involve reacting polyhydroxy compounds, such as ethylene glycol, 1,2-diols, 1,3-diols, and polyglycols, with amine compounds and hydrogen in the presence of a heterogeneous catalyst. One concern with such processes is that they can exhibit poor-to-moderate conversions and selectivities. This undesired outcome can result from the fact that the reactions can yield complex product mixtures consisting of amino alcohols, di- and tri-amines, oligomeric polyamines, cyclic amines (e.g. pyrrolidines, piperidines, and piperazines), unreacted starting materials and other unidentified compounds. Examples of these catalysts and processes can be found in U.S. Pat. Nos. 6,376,713; 6,057,442; 5,288,911; 4,123,462; 4,151,204; and 4,111,840.
Alternately, amino alcohols can be prepared by reacting an amine compound with 2-chloro-1-propanol (see, for example, JP 01056652) or by stoichiometric reduction of the corresponding amino acids and ester derivatives with a variety of reducing reagents (A. Abiko et al., Tetrahedron Lett. 1992, 33, 5517; M. J. McKennon, et al., J. Org. Chem. 1993, 58, 3568, and references therein) and by catalytic hydrogenation of amino acids, for example as reported in U.S. Pat. Nos. 5,536,879; 5,731,479; and 6,310,254. In works described by Miller, et al., (Organic Letters, 2003, 5(4), 527) on the conversion of alanine to desired products it is stressed the importance of performing hydrogenations at low pH such that the amino acid is in the protonated form rather than carboxylate form. In general, the catalytic hydrogenation of amino acids require a low solution pH in conjunction with high catalyst loading, prolonged reaction times, and high hydrogen pressure. Thus, these processes can often be costly since additional expensive feedstocks and reagents are needed.
Propylene glycol, also known as 1,2-propanediol, is a major industrial chemical with a variety of end uses. More than 400 million kilograms of propylene glycol are consumed within the United States per year. One major end use of propylene glycol is as a raw material in the manufacture of polyester resins. Propylene glycol is also used in cosmetics, personal care products, pharmaceuticals, and food applications, at least in part due to its low toxicity, absence of color and odor, excellent solvent characteristics, and good emollient properties. The United States Food and Drug Administration has determined propylene glycol to be “generally recognized as safe” (GRAS) for use in foods, cosmetics, and medicine. Other categories of use include applications as functional fluids, such as aircraft de-icing fluids, antifreezes, lubricants, inks, and heat transfer fluids, paints and coatings, plasticizers, and cellophane. Propylene glycol may also be used as a solvent and/or enzyme stabilizer in detergent applications.
Propylene glycol is commonly produced by the hydration of propylene oxide, which in turn, may be produced from propylene from petrochemical sources such as coal gas or cracking of petroleum. Thus, a large amount of propylene glycol is derived from non-renewable petroleum-based sources. Further, mixtures comprising propylene glycol and a 2-amino-1-propanol may have various uses in certain industrial processes and commercial products.
The industrial production of chemicals may be driven by economic concerns. Industrial scale production of certain chemicals requires large plant operations, oftentimes with equipment and reactors dedicated to the production of a specific chemical product. Decreasing the industrial infrastructure necessary for the production of various chemicals may result in an economic advantage to the company. For example, if a company could use specific infrastructural facilities for the production of multiple chemical end products, certain cost benefits may be realized.
Therefore, there remains a need for processes for producing a product comprising an amino alcohol and propylene glycol from inexpensive and renewable feedstocks, such as glycerol, in a cost effective manner, which can also reduce or eliminate the production of substantial amounts of undesired byproducts.